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Can’t find that rare leopard anywhere? Ask a dung beetle

Dung beetles may one day be a conservationist's best friend. Researchers already consider a healthy and diverse population of these poop-eating insects (pictured) a reliable sign of a healthy mammal population. But entomologists have now demonstrated that the beetles can reliably tell just what species are there as well. Many animals hide very well in their environments and so are hard to inventory. It might seem logical to look for their droppings instead. But animal poop is so rich that it gets quickly carted away and buried and can be as hard to find as the animals themselves. However, the researchers rationalized that mammal poop should contain blood and other cells with DNA inside, and that some of this genetic material should survive intact when eaten. So they trapped airborne dung beetles in a Swaziland savanna by hanging up a transparent sheet and selected one individual from each of 10 species to dissect. Then they removed the insects’ pooped-filled guts and sequenced all the DNA they could find there. Finally, they matched those sequences to those in existing DNA databases to learn where the DNA came from. With just 10 beetles, they showed there were blue wildebeest, zebras, mice, cattle, goats, and even humans living nearby, they report this week on bioRxiv, a preprint archive. This was a proof-of-principle study, the authors say, but dung beetles are easy to find and catch by the hundreds. And because genome sequencing is relatively cheap now, it's feasible to analyze DNA in large numbers of the beetles, and possibly to detect species—such as the critically endangered small leopard found on the Arabian Peninsula—without ever laying eyes on them.